Absorbent articles such as disposable diapers, incontinence pads, and catamenial napkins generally include an absorbent core for receiving and holding body exudates. The absorbent core typically includes a fibrous web, which can be a nonwoven, airlaid web of natural or synthetic fibers. A class of particulate absorbent materials known as superabsorbent polymers or absorbent gelling materials can be incorporated in the fibrous web to improve the absorption and retention characteristics of the fibrous web.
Because absorbent gelling materials are generally significantly more expensive than readily available natural or synthetic fiber materials (e.g., cellulose fibers), it is advantageous to reduce the quantity of absorbent gelling material in the core. Rather than uniformly reducing such particles throughout the entire core, it is desirable to distribute the particles in the absorbent core in a predetermined manner so that the particles are located where they will be most effective in acquiring and retaining body exudates.
Various techniques have been developed to distribute and locate absorbent materials on or within a fibrous substrate. U.S. Pat. No. 4,800,102 issued to Takada discloses applying a powder to the top surface of a substrate by spraying powder through an opening in a rotating disc member. Powder not passing through the opening is shown to be supported on a horizontal surface of the disc as the disc rotates, and is subsequently scraped from the disc by a scraper into a receiving member below the scraper. Powder not removed by the scraper is removed by a vacuum sucker positioned above the disc. Such an arrangement is disadvantageous because it requires powder material to accumulate on the disc. The arrangement requires a relatively complicated scraper and vacuum device to remove powder from the disc. Centrifugal forces may cause some of the accumulated powder to be flung from the disc, thereby complicating powder recycling. Powder accumulating on the disc prior to removal may also cause rotary imbalance and vibration of the disc, especially if the disc is rotated at the relatively high speeds desirable for cost effective production rates. Further, the powder material is shown to be directed generally perpendicular to the disc surface. Therefore, powder material may strike and bounce off of the disc in an unpredictable direction, thereby further complicating powder recycling.
U.S. Pat. No. 5,028,224 issued to Pieper et al. discloses pulsing and diverting mechanisms for producing an intermittent flow of absorbent particles. The diverting mechanism includes a flap which rotates about a pivot between a closed position and an open position to provide an intermittent quantity of particulate material. Such an arrangement is undesirable because operation of such a flap between the open and closed positions requires accelerating and decelerating the flap between two stationary positions. Operating such a reversing mechanism at high speeds can result in undesirable inertial forces in the mechanism, and complicates precise control of the definition of the pulse of the particulate material.
U.S. Pat. No. 5,213,817 issued to Pelley discloses a stream of powder material passing through a nozzle which is movable between first and second positions. A flow separator splits the stream into two intermittent streams as the nozzle is moved between the first and second positions. As in Pieper et al. above, such an arrangement is undesirable because operation of the nozzle between two positions requires accelerating and decelerating the nozzle between two stationary positions. Reversing the direction of motion of the nozzle at high speeds results in undesirable inertial forces, and complicates precise control of the definition of the pulse of particulate material.
Accordingly, it is an object of the present invention to provide an apparatus and method for applying discrete particles to a fibrous web. It is another object of the present invention to provide a pulse of discrete particles for application to a predetermined location on a fibrous web. Another object of the present invention is to provide a continuously rotating mask having a particle diverting surface forming an acute included angle with a supply stream of particles to split the stream of discrete particles into a first intermittent stream passing through the mask and a second intermittent stream deflected by the diverting surface.